Question

1. Observe the microstructure of three given cast irons samples (1, 2 and 3) using optical microscopy and then a) Identify each of them from their key microstructural features from micrograph. b) Specify your reasons for identification and compare their mechanical properties. c) Schematically draw the microstructures and mark all the microstructural features. ampie 1 Sample 2 100 um Sample 100 um

Answer 1

3 Simple - 1 → Nodular Cast iron cou) Cuctile Cast Sample- ¿ → Gray Cast Iran. Sample-3 . white Cast Iron. b) Sample-1 & 7. En Sample-1 Typically dosk Spheoidal nodules of graphite ane doseoved, embedded in ferrite degian (light ares] Based on this reasons we can conclude the is a Nodular cast Zoon. Sample!-2 en Sample-a we can observe the Graphite flakes* In Pearlite region. Based on thing we can conclude this as a Goay Cost Iron Sample: -3: 2 Cementite → an this Sample Pearlite i powseat in dendrotic from as an a darts colour Cemaslike * Theis peattile dendootics are present in the Gementite mastoix region. Pearlite CS Scanned with CamScanner CS Scanned with CamScanner

mechanical properties:- .! ₃. Due to large amount of Comantite at is hard r bssith -lity Sample-1 [nodular cast doon sample-2/ Samples 2 (Gray Cast Iron] ² Cwhite cast kron] 4 9. This nodillor Cast 29ou have. Excellent menimam doctility 8 machinabi machinability. & Easy to cast + poor kveldability Especiaug' cdu- → Extarmely Brittle 8 Excellent castability Qulaqous to large complex shapes difficult to wachine high modulo Elest icity. Etcellent water * Excellent wear Desislenko resistance excellent damping Poopeolies bhish compressive strength. c ) Spheral Modules of Graphite. » feorite. Scample-2 (nodular Cast Doon pearlite Graphite flakes D Sample-2 [Gray cast Iron] peastite matrix Gementtite → Peislite can bentsotic form] Cementite. Sample-3 ( White Cast Iron]. CS Scanned with CamScanner CS Scanned with CamScanner

Sample Sample - 2 0.2 wt % sted wt % sted. High carbon steed. low carbon steel 4 Reason: - most of region is White which is called al-Ferrite . * remaining very few blank regions are caked "pearlite" Reason most of region is looking black is called "pearlit kalhite region remaining is called cementite dla ferrite Realite * very soft used in structural applications. Cementite peartite a very harder. * used as cutting tools. CS Scanned with CamScanner

>o-phase (with oanvitic grains). The micoo structure of a Cast aeg Brass augs (Cu-3028) typically dendritic grain Structure with d-phase. In this case, the axis of dendroites or polyhedra Crystallize first, and are enriched with less easily mellea copper ( White area), Interfacial anego are in the last stage of crysteellizaton filled with. - Solid solution, which are very rich on zinc (darts Anees). 1 CS Scanned with CamScanner